1. Field of the Invention
The invention relates to a lubrication structure of a cranking rotational force transmission mechanism for an internal combustion engine, which transmits the rotational force of a starter motor in one rotational direction to a rotational output shaft of the internal combustion engine via a one-way clutch and interrupts the transmission of the rotational force of the starter motor in the other rotational direction via the one-way clutch.
2. Description of the Related Art
As a cranking rotational force transmission mechanism for an internal combustion engine (e.g., an internal combustion engine for a vehicle) which transmits the rotational force of a starter motor to the crankshaft (i.e., rotational output shaft) of the internal combustion engine, JP-A-2000-274337 describes a mechanism in which the ring gear and the pinion gear on the starter motor side are arranged to be constantly in mesh with each other.
In such a constantly-meshed type cranking rotational force transmission mechanism for an internal combustion engine, a one-way clutch is provided between the ring gear and the crankshaft (a flywheel is also provided between the ring gear and the crack shaft in the cranking rotational force transmission mechanism described in JP-A-2000-274337). When the starter motor cranks the internal combustion engine, the rotational force of the starter motor is transmitted to the crankshaft via the one-way clutch. Then, in response to the crankshaft starting to rotate on the force output from the internal combustion engine, the one-way clutch is released and, hence, the rotational force of the crankshaft is not transmitted to the ring gear side.
In such a cranking rotational force transmission mechanism, lubricant needs to be supplied to the one-way clutch and other rotational components to lubricate and cool them. When the internal combustion engine is running, the components on the crankshaft side, such as the flywheel, rotate, however the ring gear that is connected to the internal combustion engine via the one-way clutch does not rotate. Therefore, the lubricant tends to stagnate in the ring gear side.
The more the lubricant stagnates in the ring gear side, the higher the possibility of the surface of the stagnant lubricant being strongly agitated by the rotating one-way clutch and flywheel which are located adjacent to the ring gear. Such agitation of the lubricant surface increases the likelihood of bubbling of the lubricant and production of sludge.
If the lubricant is bubbled and sludge is produced as mentioned above, the components, such as the one-way clutch and some bearings, may be damaged due to inappropriate lubrication and cooling by the lubricant, and the sealing performances of some sealing members may deteriorate due to the sludge being caught at them.